Tetrahalidometallate(II) Ionic Liquids with More than One Metal: The Effect of Bromide versus Chloride

Fifteen N‐butylpyridinium salts – five monometallic [C(4)Py](2)[MBr(4)] and ten bimetallic [C(4)Py](2)[M(0.5) (a)M(0.5) (b)Br(4)] (M=Co, Cu, Mn, Ni, Zn) – were synthesized, and their structures and thermal and electrochemical properties were studied. All the compounds are ionic liquids (ILs) with melting points between 64 and 101 °C. Powder and single‐crystal X‐ray diffraction show that all ILs are isostructural. The electrochemical stability windows of the ILs are between 2 and 3 V. The conductivities at room temperature are between 10(−5) and 10(−6) S cm(−1). At elevated temperatures, the conductivities reach up to 10(−4) S cm(−1) at 70 °C. The structures and properties of the current bromide‐based ILs were also compared with those of previous examples using chloride ligands, which illustrated differences and similarities between the two groups of ILs.